This article proposes a new approach to investigating the substance of lawmaking. Only a very small proportion of bills become law in the U.S. Congress. However, the bills that do become law often serve as vehicles for language originating in other bills. We investigate “text reuse” methods as a means for tracing the progress of policy ideas in legislation. We then show how a focus on policy ideas leads to new insights into the lawmaking process. Although our focus is on relating content found within bills, the same methods can be used to study policy substance across many research domains.